Oil wells and wells for other fluids typically comprise a string of tubing surrounded by a well casing. The well casing is what lines the wellbore and usually comprises a long string of relatively large diameter pipe interconnected by internally threaded couplings known as collars. Casings generally define the overall diameter and depth of a wellbore. Well tubing has a much smaller diameter for fitting down inside the casing. Tubing typically comprises a long string of pipe sections whose threaded ends are also interconnected by threaded couplings. The tubing provides a conduit for conveying oil or some other fluid to the surface of the well. Usually a submerged reciprocating pump is attached to the lower end of the tubing to draw the fluid from the annulus between the inside diameter of the casing and the outside diameter of the tubing, and to force the fluid up through the tubing to the surface. To operate the pump, a string of sucker rods extends through the tubing to serve as a long reciprocating connecting rod that couples the submerged pump to a reciprocating drive unit at ground level.
Measuring the length of each casing or tubing segment before installing it down a wellbore can help establish a record of the pipe string's final overall length. This can be accomplished by simply using a tape measure to measure each joint (i.e., measure the length of a pipe segment plus one coupling attached to it) and then recording and summing the readings manually (i.e., manually tallying the readings). To minimize human error, electronic measuring systems have been developed, such as the one disclosed in U.S. Pat. No. 7,042,555, which is specifically incorporated by reference herein.